High power LEDs are commonly used in luminaires, for example, in the architectural lighting industry in stores, offices, and businesses as well as in the entertainment industry in theatres, television studios, concerts, theme parks, night clubs, and other venues. These LEDs are also being utilized in automated lighting luminaires with automated and remotely controllable functionality. For color control it is common to use an array of LEDs of different colors. For example, a common configuration is to use a mix of red, green, and blue LEDs. This configuration allows the user to create the color they desire by mixing appropriate levels of the three colors. For example, illuminating the red and green LEDs while leaving the blue extinguished will result in an output that appears yellow. Similarly, red and blue will result in magenta, and blue and green will result in cyan. By judicious control of these three controls the user may achieve nearly any color they desire. More than three colors may also be used and it is well known to add amber, cyan, or royal blue LEDs to the red, green, and blue to enhance the color mixing and improve the gamut of colors available.
The differently colored LEDs may be arranged in an array in the luminaire where there is physical separation between each LED. This separation, coupled with differences in die size and placement for each color, may affect the spread of the individual colors and results in objectionable spill light and color fringing of the combined mixed color output beam. It is common to use a lens or other optical device in front of each LED to control the beam shape and angle of the output beam; however, these optical devices commonly have differing effect for different colors and color fringing or other aberrations may be visible in the output beam. It is also known to use dichroic reflecting filters to combine three single colors of LED into a beam. However, these systems do not provide means for mixing more than three colors of LEDs. It would be advantageous to have a system which provides good homogenization of more than three colors of LEDs into a single output light beam.
There is a need for a homogenization system for an LED array based luminaire which provides improvements in homogenization for LED systems comprising four or more different colors of LEDs.